Selenium storage tube



Nov. 19, 1963 J. P. WALKER, JR 3,111,601

SELENIUM STORAGE TUBE Filed May 1a. 1960 F ATTORNEYS United StatesPatent O 3,111,601 SELENHUM STORAGE TUBE John P. Walker, Jr., SiateCollege, Pa., assigner to HRB- Snger, Inc., State College, Pa., acorporation of Dela- Ware Filed May 1s, 195o, ser. No. 29,864 s Claims.(cl. 315-) This invention relates to recording apparatus and moreparticularly to electronic storage tubes for the recording ofinformation.

Electronic storage tubes have been used to record information,particularly of a transient nature, so that the information may bereproduced at a later time or rat a slower rate and vthus be availablefor study and observation at a m'ore convenient time and speed. Suchtubes have utilized the received signals to modulate an electron beamwhich is 4focused onto the storage electrode in order to alter thecharge pattern thereon in :accordance Iwith the lelectron beammodulation land deflection. Alternatively, some electronic storage tubeshave utilized a storage medium which is sensitive to li-ght in order tostore a charge pattern thereon. In the past, reproduction of the storedsignals lwas accomplished by focusing a read-out beam of electrons ontothe storage electrode in order to detect the presence of 'a previouslyrecorded charge thereon. Due to the nature of the storage mediums,presently ntilizedtubes have not shown themselves to be entirelyreliable when operated i-n high ambient temperatures.

Accordingly, one object of this invention is to provide a novelelectronic `Storage tube utilizing la beam of light for read-out.

Another object of this invention is to provide an electronic storagetube which is economic to manufacture.

A further object of this invention is to provide an electronic storagetube which may be operated in high ambient temperatures.

In accordance with an aspect of the invention, there is provided astorage tube in which an electron beam' is Y modulated by signal energyand deflected across the face of `a Stora-ge electrode to store thesignals in the form of a charge pattern. The read-out of the storedcharge pattern is accomplished by focusing a beam of light onto thestorage electrode, thereby altering its resistance, and conducting thestored charge from the area of the target electrode illuminated 'by the"beam of light.

In accordance with another aspect of the invention, a transparentstorage electrode is utilized so that the write-in electron beam may befocused from one side of the storage electrode and the read-out lightbeam maybe focused from the opposite side of the storage electrode.

The above-mentioned and other features and objects of this inventionywill become more -apparent by reference to the following description,taken in conjunction 'with the accompanying drawing, in which:

FIG. 1 is a schematic illustration, partly in block form, ofoneembodiment of the novel electronic storage tube;

FIG. 2 is a schematic illustration of an alternative embodiment of thenovel electronic storage tube; and

FIG. 3 is an illustration of one form of storage electrode for use inthis invention.

Referring to FIG. 1 of the drawing, the novel storage tube comprises anevacuated envelope 1 containing -a target electrode 10 Iand suitableelectron gun structure 3 for producing a beam of electrons and fordirecting it through an aperture 4 in -a mirror 5 which is angularlydisposed within the envelope r1 relative to the axis of the electronbeam. The electron beam is produced by `a gun structure 3 Well kno'wn tothose skilled in this art. The electron gun 3 may include ya cathode 6heated by filament 6a and grid 7. The cathode beam is focused anddeflected 331 l Patented Nov. 19, 1963 ice target electrode 10. rllhetarget electrode 10 comprises a Y conductive signal plate 11 which iscoated with la photosensitive charge storing material 12 such asamorphous selenium. The target electrode coating should have the qualityof very low dark current preferably at high ambient temperatures and arelatively low resistance in the presence of light. Amorphous selenium`has these desired characteristics. The read-out mechanism comprisesmeans to generate a ray of light yand :deflect the ray across the targetelectrode 10. In the embodiment illustrated in FIG. 1 the read-outmechanism comprises a cathode ray tube 13 with its usual ray deflectioncircuits (not shown). The light ray from the surface of the tube 1.1i`is focused by the lens 14 and mirror 5 onto the target electrode 10.

In operation, the signals to be stored from source 15 are coupled to thegrid 7 and used to modulate the stream of electrons emitted by theelectron gun 3. The modulated stream of electrons is deected across theface of the target electrode 10 'by the deilection circuits 8 and 9. Asthe electrons impinge upon the selenium coating 12 the potential of theelemental tarea is altered and a charge is stored due to the highresista-nce of the coating.

In order to read-out the information stored on the target electrode 1i),a ray of light from the cathode ray tube 13 is focused by lens 14 :andreflected by the mirror 5 onto the target electrode 10. In the usualmanner, the ray of light from the cathode ray tube may be deflectedacross the face of the electrode 10. As light strikes an elemental areaon the electrode 10, the resistance of the coating is substantiallylowered yand if ya charge is present it is transferred to the conductiveplate 111. The transfer of a stored charge to the plate 11 under theinfluence of the read-out light causes the potential |across theresistor 30 to change and thus the :stored charge is detected. It shouldbe noted that the electronic .storage tube illustrated in FIG. 1 of thedrawing utilizes a standard cathode ray tube as the read-out structureand that the envelope 1 only contains a 'Write-in structure.

In the embodiment of this invention illustrated in FIG. 2, an electronicstorage tube containing lboth the write-in and the read-out structure isshown to include an .evacuated envelope r16 containing ya targetelect-rode 17. An electron gun structure (not shown) generates a be-amof electrons which is modulated by the signal energy to be stored in amanner described above. The modulated beam of electrons is deflected |bycoils 18 across the face of the target electrode 17. The targetelectrode 17 comprises a conductive grid or conductive glass surface 19which is coated with amorphous selenium 20. Read-out .is accomplished bygenerating a ray of light on the phosphor coated plate 21. The ray oflight on plate 21 is created by generating an electron beam lfrom a gunstructure (not shown) and allowing the electrons to activate thephosphor causing it to emit light. The spot of light on plate 21 isdeected by means of the coils 22 affecting the electron be-am. 'Ihelight from the plate 21 is focused onto the target electrode 17 by meansof the lens system 23. The focused light passes through the conductive:glass or grid signal plate 19 and alters the resistance of the seleniumcoating 20. If a charge is present on the area of the :coatingilluminated by the beam, la voltage drop is detected across the resistor24.

Referring now to FIG. 3, an alternate form of electrode is illustrated,comprising a transp-arent glass base 25 coated with stannous chloride 26to provide a transparent conductive signal plate. On top of the stannouschloride, a layer of amorphous selenium 27 is deposited to provide asignal storage medium which is photo-sensitive. ln order to alter theresistance of the photo-sensitive storage medium, the opposite side ofthe glass base 25 is coated with phosphor 28 in order to produce lightfor the readout function. The target electrode of FIG. 3 may be utilizedin the storage tube structure shown in FIG. 2.

While I have described above the principles of this invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by Way of example and not as `a limitationto the scope of this invention, as set forth in the objects thereof andin the accompanying claims.

I claim:

l. A signal storage tube system `comprising means for generating anelectron beam of energy, a target electrode including a conductivesignal plate and in intimate Contact with said signal plate, a layer ofphoto-sensitive material capable of storing a charge pattern, saidmaterial having a characteristic of high electrical resistance in theabsence of light and a relatively low electrical resistance in thepresence of light, means for scanning said target electrode with saidbeam of energy to store a charge pattern on said material, 4means forgenerating a beaml of light, means for scanning said target electrodewith said beam of light whereby the charge stored on said material iscoupled to said signal plate when said electrode is illuminated by saidbeam of light, and means coupled to said signal plate to detect thecharge coupled thereto from said materia under the inuence of said Ibeamof light.

2. A Isignal storage tube system comprising a target electrode includinga conductive signal plate and in intimate surface contact with saidsignal plate, a layer of photosensitive material capable of storing acharge pattern, said material having the `characteristic of highelectrical resistance in the absence of light and relatively lowelectrical resistance in the presence of light, an electron gunstructure -for generating a stream of electrons, means for modulatingsaid stream of electrons ywith the signals to be stored, means to cause`said modulated stream of electrons to scan said target electrode in apredetermined pattern to cause a charge to be stored thereon, `a sourceof light, means to focus said light on said target, electrode means to`cause said light to scan said target electrode in a predeterminedpattern, and means to couple from said signal plate the stored signalscoupled from said layer of 4 material to said signal plate under theinfluence of said light.

3. A storage tube system according to claim 2 wherein said signal plateis transparent and said light is focused onto one side of said plate`and said layer of material is disposed on the opposite side of saidplate.

4. A storage tube system in accordance with claim 2 wherein said signalplate is composed of a conductive grid and said layer olf material coatssaid grid.

5. A storage tube system in accordance with claim 2 wherein said sourceof light includes a cathode ray tube.

6. A storage tube system in accordance With claim 5 which furtherincludes a mirror disposed Iat an angle to the axis of said electronstream, said mirror having an aperture through which said electronstream is focused, and said cathode ray tube being disposed at an angleto said electron stream axis and the light from said cathode ray tubereflected by said mirror onto said target electrode.

7. A storage tube system `comprising a target electrode including atransparent conductive signal plate and in intimate surface contactwit-h said plate, a layer of photosensitive material capable of storinga charge pattern, said material having the characteristic of rhighelectrical resistance in t-he absence of light and low electricalresistance in the prseence of light, an electron gun structure forgenerating a stream of electrons, means to modulate said electron streamwith the signals to be stored, means t0 cause said modulated elect-ronstream to scan said target electrode in a predetermined pattern to causea charge to be stored thereon, a photo-emissive electrode, means tocause said photoemissive electrode to generate a beam of light, means tofocus said light onto said target electrode, and means to couple signalsfrom said signal plate which lare coupled from said layer of ymaterialunder the inlluence of said light.

8. A signal storage tube system according to claim 7, wherein saidtarget electrode includes a transparent lbase, a layer of stannouschloride disposed on said base and a layer of amorphous selenium on saidstannous chloride.

Harsh Feb. 4, 1958 Ploke et al Nov. 25, 8

1. A SIGNAL STORAGE TUBE SYSTEM COMPRISING MEANS FOR GENERATING ANELECTRON BEAM OF ENERGY, A TARGET ELECTRODE INCLUDING A CONDUCTIVESIGNAL PLATE AND IN INTIMATE CONTACT WITH SAID SIGNAL PLATE, A LAYER OFPHOTO-SENSITIVE MATERIAL CAPABLE OF STORING A CHARGE PATTERN, SAIDMATERIAL HAVING A CHARACTERISTIC OF HIGH ELECTRICAL RESISTANCE IN THEABSENCE OF LIGHT AND A RELATIVELY LOW ELECTRICAL RESISTANCE IN THEPRESENCE OF LIGHT, MEANS FOR SCANNING SAID TARGET ELECTRODE WITH SAIDBEAM OF ENERGY TO STORE A CHARGE PATTERN ON SAID MATERIAL, MEANS FORGENERATING A BEAM OF LIGHT, MEANS FOR SCANNING SAID TARGET ELECTRODEWITH SAID BEAM OF LIGHT WHEREBY THE CHARGE STORED ON SAID MATERIAL ISCOUPLED TO SAID SIGNAL PLATE WHEN SAID ELECTRODE IS ILLUMINATED BY SAIDBEAM OF LIGHT, AND MEANS COUPLED TO SAID SIGNAL PLATE TO DETECT THECHARGE COUPLED THERETO FROM SAID MATERIAL UNDER THE INFLUENCE OF SAIDBEAM OF LIGHT.